Yoshio Ohnishi

Onset heart rate of microvolt-level T-wave alternans provides clinical and prognostic value in nonischemic dilated cardiomyopathy.

OBJECTIVES This study was designed to determine the prognostic value of onset heart rate (OHR) in T-wave alternans (TWA) in patients with nonischemic dilated cardiomyopathy (DCM). BACKGROUND One of the current major issues in DCM is to prevent sudden cardiac death (SCD). However, the value of the OHR of TWA as a prognostic indicator in DCM remains to be elucidated. METHODS We prospectively investigated 104 patients with DCM undergoing TWA testing. The end point of this study was defined as SCD, documented sustained ventricular tachycardia/ventricular fibrillation. Relations between clinical parameters and subsequent outcome were evaluated. RESULTS Forty-six patients presenting with TWA were assigned to one of the following two subgroups according to OHR for TWA of < or = 100 beats/min: group A (n = 24) with OHR < or = 100 beats/min and group B (n = 22) with 100 < OHR < or = 110 beats/min. T-wave alternans was negative in 37 patients (group C) and indeterminate in 21 patients. The follow-up result comprised 83 patients with determined TWA. During a follow-up duration of 21 +/- 14 months, there was a total of 12 arrhythmic events, nine of which included three SCDs in group A, two in group B and one in group C. The forward stepwise multivariate Cox hazard analysis revealed that TWA with an OHR < or = 100 beats/min and left ventricular ejection fraction were independent predictors of these arrhythmic events (p = 0.0001 and p = 0.0152, respectively). CONCLUSIONS The OHR of TWA is of additional prognostic value in DCM.

Determinant of microvolt-level T-wave alternans in patients with dilated cardiomyopathy

OBJECTIVES The aim of this study was to clarify the clinical significance and the determinant of microvolt-level T-wave alternans (TWA) in patients with dilated cardiomyopathy (DCM). BACKGROUND The prevention of sudden death in patients with DCM remains the therapeutic target. T-wave alternans has been proposed as a powerful tool for identification of patients at high risk for ventricular arrhythmias and sudden death in coronary artery disease. METHODS In 58 DCM patients, TWA was measured during bicycle exercise testing using a CH 2000 system (Cambridge Heart, Bedford, Massachusetts). The New York Heart Association class, signal-averaged electrocardiogram, QT dispersion, left ventricular end-diastolic diameter (LVDd) and percent fractional shortening detected by echocardiogram and the grade of the ventricular arrhythmia were obtained in all patients. RESULTS T-wave alternans was positive in 23 patients (TWA+ group), negative in 25 (TWA- group) and indeterminate in 10. Univariate analysis showed that the percentage of patients with ventricular tachycardia (VT) and the LVDd in the TWA+ group was significantly higher than those in the TWA- group (61% vs. 8%, p < 0.001 and 65 +/- 11 mm vs. 58 +/- 8 mm, p < 0.05, respectively). The sensitivity, specificity and predictive accuracy of TWA for VT were 88%, 72% and 77%, respectively. Multivariate analysis showed that the presence of VT was a major independent determinant of TWA in patients with DCM (p = 0.003). CONCLUSIONS T-wave alternans was closely related to VT in patients with DCM. T-wave alternans is a useful noninvasive test for identifying high risk patients with DCM who have VT.

Usefulness of beat-to-beat QT dispersion fluctuation for identifying patients with coronary heart disease at risk for ventricular arrhythmias

QT dispersion (QTd) has been proposed as a marker of ventricular repolarization inhomogeneity and arrhythmic risk, but despite the dynamic properties of ventricular repolarization and the fact that QTd represents only a static parameter of the repolarization event, beat-to-beat QTd behavior has not been assessed so far. Beat-to-beat QTd was automatically measured in 12-lead digitized electrocardiographic recordings obtained over 10 minutes from 77 subjects. Forty-seven patients had coronary heart disease without a history of ventricular arrhythmias, 12 had coronary heart disease and documented ventricular tachycardia, and 18 were normal subjects. Mean QTd, the difference between the maximum minus the minimum QTd observed over the recording time (QTd variation), the maximum difference of QTd between consecutive beats (QTd maximum), and QTd SD (QTd variability) were analyzed between groups. The temporal QTd parameters were significantly increased in the group of patients with susceptibility to ventricular arrhythmias compared with those in both healthy subjects (QTd variation p <0.0001, QTd maximum p <0.001, QTd variability p <0.0001) and patients without a history of ventricular tachycardia (QTd variation p <0.01, QTd maximum p <0.01, QTd variability p <0.01). Mean QTd was also significantly increased in the groups of patients with and without ventricular tachycardia compared with controls (p <0.001 and <0.01), but did not differ significantly between the 2 patient groups. Thus, QTd has a dynamic behavior with significant beat-to-beat fluctuations even in normal subjects and is more marked in patients with coronary heart disease at risk for ventricular arrhythmias.

Dispersion of the monophasic action potential duration in patients with polymorphic ventricular tachycardia.

Abstract The mechanism of polymorphic ventricular tachycardia (PMVT) remains unclear. To investigate the electrophysiologic mechanism of PMVT, monophasic action potentials (MAPs) were recorded with a contact electrode technique from right ventricular sites during sinus rhythm and right ventricular pacing. MAPs were obtained from 6 patients with PMVT (PMVT group) and II patients without PMVT (control group). The duration from the onset of the upstroke to 90% repolarization of the MAP (MAPD90) during right ventricular pacing at both pacing cycle lengths of 600 and 400 ms was significantly longer in the PMVT group than in the control group (332 ± 60 ms vs 279 ± 33 ms [P

The Efficacy and Safety of Open Irrigation Catheter in Pulmonary Vein Isolation for Atrial Fibrillation

Background: Open irrigation Catheter (OIC) have the advantage of delivering greater power without increasing the temperature of the catheter tip, which can ablate wider and deeper lesions, compared with conventional tip catheter. We study the efficacy and safety of OIC for pulmonary vein isolation (PVI) for atrial fiblillation (AF). Method: Catheter ablation was performed using 3.5 mm OIC (Navistar ThermoCcool) or 8-mm catheter (8MC, Navistar DS). Seventy one consecutive AF patients (60 males, 60.6±15 years, 66 paroxysmal AF, 5 persistent AF) enrolled in the study, and subdivided into two groups, OCI group (n=29) and 8MC group (n=42). PVI was performed with maximum power 35 W at 17 or 30 ml/min of constant saline infusion in OCI group. Result: Isolation of pulmonary vein was achieved in all patients. Fluoroscopy time and the number of energy application have no differerce between two groups (respectively, 144 vs 133 min, p=0.286, 96.8 vs 96.3 p=0.57). The recurrence of AF was significant lower in OIC group compared with 8MC group (48% vs 17%, p=0.0045) during mean 3.5 months follow up period with 2 months blanking period. There was no major complication. However, lung congestion without dyspnea in 3 patients and small cerebral infarction in 1 patient in OIC group after procedure. Conclusion: Although there was a lower rate of AF recurrence with the use of OIC, the setting was associated with increased congestive heart failure due to the volume overload.